1. Field of the Invention
The present invention relates generally to intra-aortic balloon pump type devices (xe2x80x9cIABPxe2x80x9d) that act as a left ventricular assist devices (xe2x80x9cLVADxe2x80x9d) as well as to related devices which assist in maintaining a patient""s cardiac output when the normal cardiac output is not sufficient to maintain an adequate pressure for supplying the patient""s organs with arterial blood.
2. Description of the Prior Art
The intra-aortic balloon pump (xe2x80x9cIABPxe2x80x9d) is by far the most commonly utilized left ventricular assist device (xe2x80x9cLVADxe2x80x9d). This device is used when the patient""s cardiac output is not sufficient to maintain an adequate arterial blood supply to the patient""s organs.
The IABP consists of an inflatable balloon attached to a catheter, which is advanced through the patient""s femoral artery and into the descending aorta. Inflation and deflation of the balloon is accomplished by an external control unit synchronized with the heart beat. This unit rapidly inflates the balloon during the diastolic or resting phase of the heart cycle, and thus elevates diastolic aortic blood pressure and improves blood flow to the heart, the brain and other tissues. The balloon is rapidly deflated as the heart contracts. This reduces the aortic blood pressure that the heart must overcome to eject blood from the left ventricle. Thus, the IABP is a LVAD that also augments diastolic aortic blood pressure.
However, present IABP devices cannot sustain the circulation if the heart is severely diseased or injured, since ventricular ejection must be sufficient to keep the mean aortic blood pressure above approximately 60 mmHg. When the aortic pressure falls below this value, there is insufficient blood to fill the space around the balloon when it is deflated. In that case the wall of the aorta collapses around the deflated balloon of prior art devices, and the IABP becomes ineffective. Thus, present IABP devices can be used only in less severe cases of left ventricular failure.
In one aspect, the present invention is directed towards improving the usefulness of IABP devices by enhancing the use of a single balloon in the descending aorta with a second, external balloon located outside the body and in direct communication with the blood within the aorta through a hollow catheter tube connecting both balloons. Although several IABP devices have used multiple balloons to enhance circulation, none use an external balloon working cooperatively with the internal balloon. Gabbay (U.S. Pat. No. 4,527,549) discloses the use of a balloon within the ascending aorta and multiple smaller balloons within the aortic arch and descending aorta. Given the difficulty in positioning a balloon within the ascending aorta with a catheter coming up from the descending aorta, the Gabbay device is cumbersome and difficult to operate. More importantly, the Gabbay device has the disadvantage of being positioned in the ascending aorta in order to function, thus increasing the chance of producing emboli that can cause problems such as stroke. Choy et al. (U.S. Pat. No. 4,902,273) discloses a dual balloon device, but which operates by a completely different mode. In the Choy et al. device, one balloon enters the left ventricle of the heart and another balloon enters the right ventricle of the heart. In a diseased heart, which may already be dilated, this would excessively expand the ventricle and may cause rupture or other permanent damage. Positioning the balloons in that invention is also cumbersome, making the device impractical for many applications.
In another aspect of the present invention, an internal catheter, rather than an internal balloon, cooperates with an external balloon located outside the body and in direct communication with the blood in the aorta.
Both aspects of the invention are intended to address the need for a device of the above type that has greater pumping capacity, that is simple to use and capable of rapid insertion and operation in an emergency situation, and that is capable of elevating blood pressure within the ascending aorta even if the descending aorta should collapse. The present invention is directed towards such a device or devices.
One object of the present invention is to provide a means and method for enhancing heart function when the blood pressure within the aorta is insufficient to prevent the collapse of the descending aorta around an intra-aortic balloon.
Another object of the present invention is to enhance the blood flow to the heart, brain, and other tissues under the conditions of poor heart function.
Another object of the present invention is to provide a means for enhancing the pumping and sucking effect of an IABP within the aorta by using a simple, unitary device that is self contained and easy to use.
Yet another object of the present invention is to provide a means of enhancing the perfusion of other arteries such as the renal arteries and the aortic arch arteries.
Yet another object of the present invention is to provide a device that acts cooperatively through a continuous unit, the size of which can be varied to adapt to the size of the patient or the desired amount of pumping.
These objects are achieved in the present invention by an intra-aortic circulatory enhancing apparatus for use in human patients to improve blood flow to other arteries continuous with the aorta of the patient. The apparatus comprises an internal inflation means located within the aorta of the patient and an external inflation means located outside of the patient. The internal inflation means can be an internal balloon coupled to a hollow extent which is operatively coupled to a blood communication means. The blood communication means can be a first hollow catheter tube in one embodiment. The external inflation means can be an external balloon coupled to a hollow extent running through the center of the balloon and continuous with a second hollow catheter tube. The blood communication means is coupled to the internal and external inflation means, allowing blood within the aorta to communicate with the secondary inflation means. Further, a pressurization means for pressurizing and depressurizing the internal and external balloons is provided. The pressurization control means is a lumen in one embodiment of the invention, the lumen associated with the balloons and extending from the balloons to be coupled to an external control unit. When operating, the balloons pump simultaneously, then draw or suck blood simultaneously, thus helping to generate blood flow. The balloons pressurize and depressurize simultaneously, thus acting cooperatively to enhance the blood-pumping action of a diseased human heart and enhance blood flow to the heart, brain, and other tissues.
In another embodiment of the invention, the external balloon itself communicates with the blood communication means. The external balloon is located within a relatively rigid sheath or housing so that by alternately applying pressure and vacuum to the interior of the housing, the external balloon can be acted upon to thereby either draw or suck blood into the blood communication means and into the external balloon.
In other embodiments of the invention, the upper balloon is merely a retaining balloon which helps to position and retain a perforated catheter, the perforations serving as the entry points for blood entering the blood communication means and leading to the external inflation means.
Additional objects, features and advantages will be apparent in the written description which follows.